Radiation method and apparatus for radiating a fluence map having zero fluence region

ABSTRACT

The present disclosure provides a radiation method for radiating a fluence map having a zero-fluence region under a movement of MLC (Multi-Leaf Collimator) includes a determining step of determining at least one basic fluence map from the fluence map. The basic fluence map includes a first non-zero fluence region and a second non-fluence region having the zero-fluence region therebetween. The radiation method includes a first radiating step including radiating the first non-zero fluence region, along with moving a first group of leaf pairs and moving a vertical jaw to shade the first group of leaf pairs, and a second radiating step including radiating the second non-zero fluence region, along with moving a second group of leaf pairs and withdrawing the vertical jaw to expose the second group of leaf pairs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/394,829, filed on Dec. 30, 2016, which in turn claims priority ofChinese Patent Application No. 201511024949.6 filed Dec. 30, 2015, thecontents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to radiation method and anapparatus used in radiation therapy, and more particularly, a radiationmethod for a fluence map having zero fluence region and an apparatusthereof.

BACKGROUND

Along with the development of medical theories such as the radiophysics,radiobiology, clinical oncology etc., together along with thedevelopment of medical imaging apparatus and computer technology,radiotherapy (hereinafter referred as RT) technology is continuouslydeveloped to satisfy clinic requirement better. Due to a greatdevelopment from conventional RT technology to 3D conformal radiationtherapy (3DCRT), RT technology becomes more precise. Therefore, both apartial recurrence rate of tumor and an occurrence rate of normal tissuecomplication are greatly reduced. Intensity-modulated radiation therapy(IMRT), developed on 3DCRT, is able to conform radiation to the size,shape and location of a target region more precisely, to protect OAR(Organ At Risk) around the target region more effectively.

A basic principle of IMRT is dividing the radiation field (beam field)into multiple small segment fields (beam lets) with differentintensities to thereby optimize radiation delivery. In this way, theintensity of a beamlet through OAR is reduced while the intensity of abeamlet through the target region is increased. Multi-leaf collimator(MLC) is introduced to radiate a fluence map in IMRT. Especially to atarget region having a recess in which OAR is positioned, IMRTtechnology can be performed more effectively.

The fluence map used in IMRT is possibly shaped into a U-shape or anO-shape, to leave a recess for OAR. The fluence map is discretized withzero fluence region and non-zero fluence region, as shown in FIG. 1. Itis called subsectional fluence distribution.

According to conventional field dividing radiation method, in order toradiate the radiation field having subsectional fluence distribution,the radiation field is divided into two or more segment fields. Firstly,one segment field is radiated. Subsequently, jaws and MLC are moved tothe next segment field when radiation is closed. Jaws comprises parallelJaws moving along a direction parallel to a moving direction of the MLC,and perpendicular jaws moving along a direction perpendicular to themoving direction of the MLC.

FIGS. 15(a)-15(f) are schematic figures showing a process of radiating aU-shaped fluence map with the conventional field-dividing method.Firstly, the left half of the fluence map is radiated. When the lefthalf of the fluence map has finished to be radiated, the jaws and theMLC are moved to the right half of the fluence map. In the process ofmoving the jaws and MLC, the radiation is closed and the fluence map isnot radiated. When the jaws and MLC have been moved to the right half ofthe fluence map, the right half of the fluence map begins to beradiated.

However, the field-dividing method may have some defects. In the method,a beam field may be divided into a plurality of segment fields.Radiation of the plurality of segment fields may increase total MU. Forexample, the total MU (Monitor Unit) may increase approximately one timeto the original minimum total MU once one beam field is added. Besides,if radiation of a segment field is completed, the jaws and the MLC maymove to next segment field. The moving of the jaws and the MLC may taketime. The time spent on the moving may be referred as a ‘set-up time’.The total treatment time may be increased accordingly. Further, theremay be penumbra at the edge of segment field. Thus, doses delivered atthe edge of adjacent segment fields may be inaccurate.

SUMMARY

The objective of present invention is to provide a radiation method andapparatus for radiating a fluence map having zero-fluence regions oncefor reducing MU and save the time of treatment.

In one embodiment of the present invention, a radiation method forradiating a fluence map having a zero-fluence region under a movement ofMLC includes a determining step of determining a basic fluence map fromthe fluence map. The basic fluence map comprises at least one regiongroup each having a first non-zero fluence region and a secondnon-fluence region have the zero fluence region positioned therebetween.The radiation method further includes a first radiating step includingradiating the first non-zero fluence region, along with moving a firstgroup of leaf pairs of the MLC in the first non-zero fluence region andmoving a vertical jaw to shade the first group of leaf pairs. Theradiation method further includes a second radiating step includingradiating the second non-zero fluence region, along with moving a secondgroup of leaf pairs of the MLC in the second non-zero fluence region andwithdrawing the vertical to expose the second group of leaf pairs.

In one embodiment of the present invention, in the first radiating step,the vertical jaw is moved along a vertical direction perpendicular tothe moving direction of the first group of leaf pairs to shade part ofthe first group of leaf pairs which have finished to play a part inradiating the first non-zero fluence region in sequence.

In one embodiment of the present invention, in the first radiating step,the vertical jaw is moved along a vertical direction perpendicular tothe moving direction of the first group of leaf pairs to shade part ofthe first group of leaf pairs which have finished to play a part inradiating the first non-zero fluence region in sequence.

In one embodiment of the present invention, in the second radiatingstep, the vertical jaw is withdrawn along the vertical direction toexpose the second group of leaf pairs which begin to play a part inradiating the second non-zero fluence region in sequence.

In one embodiment of the present invention, the first group of leafpairs and the second group of leaf pairs are at least partly same.

In one embodiment of the present invention, the basic fluence mapfurther comprises a third non-fluence region communicating with thefirst non-zero fluence region and the second non-zero fluence region.The first radiating step further includes radiating a first part of thethird non-zero fluence region along with moving a third group of leafpairs of the MLC in the third non-zero fluence region. The secondradiating step further includes radiating a second part of the thirdnon-zero fluence region along with moving the third group of leaf pairsin the third non-zero fluence region.

In one embodiment of the present invention, said basic fluence map is ofa substantially U-shape and comprises one said region group.

In one embodiment of the present invention, a vertical dimension of thefirst non-zero fluence region is identical to that of second non-zerofluence region, and the number of the first group of leaf pairs isidentical to that of the second group of leaf pairs.

In one embodiment of the present invention, a vertical dimension of thefirst non-zero fluence region is greater than that of second non-zerofluence region, and the number of the first group of leaf pairs isgreater than that of the second group of leaf pairs.

In one embodiment of the present invention, a vertical dimension of thefirst non-zero fluence region is smaller than that of second non-zerofluence region, and the number of the first group of leaf pairs is lessthan that of the second group of leaf pairs.

In one embodiment of the present invention, the basic fluence map is ofa X-shape and comprises two region groups. The first radiating stepincludes radiating the first non-zero fluence region of each regiongroup along with moving the vertical jaw. The second radiating stepincludes radiating the second non-zero fluence region of each regiongroup along with the moving the vertical jaw.

In one embodiment of the present invention, the radiation method furthercomprises a further radiating step of radiating a middle part betweenthe first part and the second part of the third non-zero fluence regionhappened between the first radiating step and the second radiating step.

In one embodiment of the present invention, the radiation method furthercomprises a moving step of moving the first group of leaf pairs into aninitial position of the first non-zero fluence region before the firstradiating step.

In one embodiment of the present invention, a radiation method forradiating a fluence map having a zero-fluence region under a movement ofMLC includes a dividing step of dividing the fluence map into a numberbasic fluence maps. The basic fluence map comprises at least one regiongroup each having a first non-zero fluence region and a secondnon-fluence region having the zero-fluence region positionedtherebetween. The radiation method further includes a radiating step ofradiating each basic fluence map. The radiating step includes a firstradiating step including radiating the first non-zero fluence region,along with moving a first group of leaf pairs of the MLC in the firstnon-zero fluence region and moving a vertical jaw along a verticaldirection perpendicular to the moving direction of the first group ofleaf pairs to shade the first group of leaf pairs. The radiation methodfurther includes a second radiating step including radiating the secondnon-zero fluence region, along with moving a second group of leaf pairsof the MLC in the second non-zero fluence region and withdrawing thevertical jaw along the vertical direction to expose the second group ofleaf pairs.

In radiating each basic fluence map, the first and second groups of leafpairs are moved along an invariable direction and the basic fluence mapis radiated once. In radiating the plurality of basic fluence maps, thefirst and second groups of leaf pairs are moved repeatedly in radiatingdifferent basic fluence maps.

In one embodiment of the present invention, the first group of leafpairs and the second group of leaf pairs are at least partly same. Inthe first radiating step, the vertical jaw is moved along a verticaldirection perpendicular to the moving direction of the first group ofleaf pairs to shade part of the first group of leaf pairs which havefinished to play a part in radiating the first non-zero fluence regionin sequence. In the second radiating step, the vertical jaw is withdrawnalong the vertical direction to expose part of the second group of leafpairs which begin to play a part in radiating the second non-zerofluence region in sequence.

In one embodiment of the present invention, the basic fluence mapfurther comprises a third non-fluence region communicating with thefirst non-zero fluence region and the second non-zero fluence region.The first radiating step further includes radiating a first part of thethird non-zero fluence region along with moving a third group of leafpairs of the MLC in the third non-zero fluence region. The secondradiating step further includes radiating a second part of the thirdnon-zero fluence region along with moving the third group of leaf pairsin the third non-zero fluence region.

In one embodiment of the present invention, the basic fluence map is ofa substantially U-shape and comprises one region group.

In one embodiment of the present invention, the basic fluence map is ofa substantially X-shape and comprises two said region groups. The firstradiating step includes radiating the first non-zero fluence region ofeach region group along with moving the vertical jaw. The secondradiating step includes radiating the second non-zero fluence region ofeach region group along with the moving the vertical jaw.

In one embodiment of the present invention, a radiating apparatusapplied in radiating a fluence map having a zero-fluence region under amovement of MLC includes a determining module and a driving module. Thedetermining module is used to determine at least one basic fluence mapfrom the fluence map. The basic fluence map is adapted for beingradiated once along an invariable direction and comprises a firstnon-zero fluence region and a second non-fluence region having thezero-fluence region positioned therebetween. The driving module is usedto drive a first group of leaf pairs of the MLC to move in the firstnon-zero fluence region, moving the vertical jaw along a directionperpendicular to the moving direction of the first group of leaf pairsto shade the first group of leaf pairs, driving a second group of leafpairs of the MLC move in the second non-zero fluence region, andwithdrawing the vertical jaw to expose the second group of leaf.

As compared with prior art, the fluence map in the present invention canbe radiated once, rather than be radiated several times. MU iscorrespondingly reduced. In addition, it will be more efficiently toradiate the fluence map of the present invention, since the “set-uptime” is saved. The treatment time may be reduced accordingly.Furthermore, the fluence map is radiated once, dose delivered at theedge of adjacent fluence region is accurate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting exemplaryembodiments, in which like reference numerals represent similarstructures throughout the several views of the drawings, and wherein:

FIG. 1 is a schematic figure of 1-D of a fluence map having a zerofluence region;

FIG. 2(a) is a schematic figure showing a convex-shaped fluence map;

FIG. 2(b) is a schematic figure showing a substantially U-shaped fluencemap;

FIG. 2(c) is a schematic figure showing a substantially X-shaped fluencemap;

FIG. 3 is a schematic figure of jaws and MLC;

FIG. 4 is a schematic figure of the substantially U-shaped fluence mapcomprising a first through third non-zero fluence regions;

FIGS. 5(a)-5(g) are schematic figures showing a process of radiating thesubstantially U-shaped fluence map referred in a first embodiment of thepresent invention;

FIG. 6 is a flowchart showing the process of radiating the fluence mapshown in FIGS. 5(a)-5(g) referred in the first embodiment of the presentinvention;

FIG. 7 is a schematic figure of the substantially U-shaped fluence mapreferred in a second embodiment comprising a first and second non-zerofluence regions;

FIG. 8 is a flowchart showing a process of radiating the fluence mapreferred in the second embodiment of the present invention;

FIG. 9 is a flowchart showing a process of radiating the fluence mapreferred in a third embodiment of the present invention;

FIG. 10 is a flowchart showing a process of radiating a substantiallyX-shaped fluence map having two zero-fluence regions referred in afourth embodiment of the present invention;

FIGS. 11(a)-11(c) are schematic figures showing a C-shaped fluence mapdivided into several basic fluence maps in a fourth embodiment;

FIGS. 12(a)-12(c) are schematic figures showing an O-shaped fluence mapdivided into several basic fluence maps in a fifth embodiment;

FIGS. 13(a)-13(d) are schematic figures showing a fluence map having acomplicated shape divided into several basic fluence maps in the fifthembodiment;

FIG. 14 is a flowchart of primary steps of the radiation method referredin the fifth embodiments; and

FIGS. 15(a)-15(f) are schematic figures showing a process of theconventional field-dividing method.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirits andscope of the present disclosure. Thus, the present disclosure is notlimited to the embodiments shown, but to be accorded the widest scopeconsistent with the claims.

It will be understood that the term “system,” “unit,” “module,” and/or“block” used herein are one method to distinguish different components,elements, parts, section or assembly of different level in ascendingorder. However, the terms may be displaced by other expression if theymay achieve the same purpose.

It will be understood that when a unit, module or block is referred toas being “on,” “connected to” or “coupled to” another unit, module, orblock, it may be directly on, connected or coupled to the other unit,module, or block, or intervening unit, module, or block may be present,unless the context clearly indicates otherwise. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items.

The terminology used herein is for the purposes of describing particularexamples and embodiments only, and is not intended to be limiting. Asused herein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “include,”and/or “comprise,” when used in this disclosure, specify the presence ofintegers, devices, behaviors, stated features, steps, elements,operations, and/or components, but do not exclude the presence oraddition of one or more other integers, devices, behaviors, features,steps, elements, operations, components, and/or groups thereof.

In order to clearly understand the objective, features, and advantagesof the present invention, the embodiments of the present invention aredescribed in combination with the companying drawings as follows.

In the following description, more details are described forunderstanding the present invention fully, but other embodimentsdifferent from the recitation here also can be used by the presentinvention. Therefore, the present invention is not limited by thespecific embodiments disclosed hereinafter.

The embodiment of the present invention recites a radiation methodradiating a fluence map having zero fluence region and the apparatusused in the radiation method, which is adapted for being applied inIMRT. It is possible to radiate a fluence map having zero fluence regiononce.

FIGS. 2(a)-2(c) show three types of basic shapes of the fluence map.FIG. 2(a) shows a convex-shaped fluence map having a convex-shapedcontour without any recess. No subsectional fluence distribution isformed in the convex-shaped fluence map. In conjunction with FIG. 3, theconvex-shaped fluence map can be radiated under the movement of the MLC310 only, without a participation of the vertical jaw.

FIG. 2(b) shows a substantially U-shaped fluence map having a firstrecess opened upwardly. Optionally, the first recess can be openeddownwardly. The first recess has a zero fluence region formed therein.Subsectional fluence distribution is formed along a moving direction ofthe MLC 310. It is impossible to radiate the substantially U-shapedfluence map under the movement of the MLC 310 directly due to thesubsectional fluence distribution. The substantially U-shaped fluencemap can be divided into a non-zero fluence region S1 in front of thefirst recess, a non-zero fluence region S2 behind the first recess, anda non-zero fluence region S3 below the first recess. A zero fluenceregion is positioned between the non-zero fluence region S1 and thenon-zero fluence region S2 along the moving direction of the MLC 310, oralong a direction substantially parallel to the moving direction of theMLC 310. The non-zero fluence region S3 communicates with the non-zerofluence region S1 and the non-zero fluence region S2 along a directionperpendicular to the moving direction of the MLC 310. The substantiallyU-shaped fluence map, as shown in FIG. 2(b), needs to be radiated underthe cooperation of the MLC 310 and one perpendicular jaw 320 movingalong a direction perpendicular to the moving direction of the MLC 310.

FIG. 2(c) shows a substantially X-shaped fluence map having an upperrecess opened upwardly and a lower recess opened downwardly. The upperrecess and the lower recess respectively have a zero fluence regionformed therein. Subsectional fluence distribution is formed along themoving direction of the MLC 310, or along a direction parallel to themoving direction of the MLC 310. It is impossible to radiate thesubstantially U-shaped fluence map under the movement of the MLC 310directly due to the subsectional fluence distribution. The substantiallyX-shaped fluence map can be divided into a non-zero fluence region S4 infront of the upper recess, a non-zero fluence region S5 behind the upperrecess, a non-zero fluence region S6 in front of the lower recess, anon-zero fluence region S7 behind the lower recess, and an eighthnon-zero fluence region communicating with the non-zero fluence regionsS4-S7. A zero fluence region is positioned between the non-zero fluenceregion S4 and the non-zero fluence region S5 along the moving directionof MLC 310, or along a direction substantially parallel to the movingdirection of MLC 310. Another zero fluence region is positioned betweenthe non-zero fluence region S6 and the non-zero fluence region S7 alongthe moving direction of MLC 310, or along a direction substantiallyparallel to the moving direction of MLC 310. The substantially X-shapedfluence map, as shown in FIG. 2(c), needs to be radiated under thecooperation of the MLC 310 and two perpendicular jaws 320 moving along adirection perpendicular to the moving direction of MLC 310.

Referring to FIG. 3, MLC 310 comprises a plurality leaf pairs 312movable along a direction X. Each pair of leaves 312 are movable alongthe direction X as marked in FIG. 3. Each leaf pair 312 can be openedand folded to control a size of an opening therebetween. When the leafpair 312 is closed, there is a gap existed between the leaf pair 312 toavoid the leaves colliding each other. The parallel jaw 320 moves alongthe direction X parallel to a moving direction of the leaf pair 312. Theperpendicular jaw 330 moves along the direction Y perpendicular to amoving direction of the leaf pair 312. The leaf pair 312 of the MLC 310can be shaded by the parallel jaws 320 and the perpendicular jaws 330.In common radiotherapy apparatus, the parallel jaws 320 andperpendicular jaws 330 are used to confine the range of the radiationfield, for example, to confine a rectangular range. Furthermore, in thisrange, a contour of the radiation field is defined by multiple leafpairs of the MLC 310. In all of the embodiments of the presentinvention, contour of the radiation field is confined by multiple leafpairs 312 of the MLC 310 together with the perpendicular jaws 330.

In a first embodiment, a process of radiating a substantially U-shapedfluence map shown in FIG. 4 is illustrated below. A substantiallyU-shaped fluence map can be divided into a non-zero fluence region A infront of a zero fluences region, a non-zero fluence region B behind thezero fluences region, and a non-zero fluence region C below the zerofluences region. The non-zero fluence region A is separated from thenon-zero fluence region B by the zero fluence region along the movingdirection of the MLC 310. The non-zero fluence region C communicateswith the non-zero fluence region A and the non-zero fluence region Balong a direction perpendicular to the moving direction of the MLC 310.

FIG. 6 is a flowchart showing a process of radiating the substantiallyU-shaped fluence map having the zero fluence region referred in thefirst embodiment. FIGS. 5(a)-5(g) are schematic figures showing aprocess of radiating the substantially U-shaped fluence map of the firstembodiment. Referring to FIG. 5(a), in a step 701, a first group of leafpairs 313 utilizable in radiating the first non-zero fluence region Aare moved to an initial position Pa of the first non-zero fluence regionA. A third group of leaf pairs 316 utilizable in radiating a left halfof the third non-zero fluence region C are moved to a left edge of thethird non-zero fluence region C.

In the step 702, the first non-zero fluence region A is radiated fromleft to right gradually through an upper part of the opening between theleaves of the leaf pairs 313 in the first group, along with the movementof the leaf pairs 313 and the downwardly movement of the vertical jaw330. Meanwhile, the left half of the third non-zero fluence region C isradiated from left to right gradually through the lower part of theopening between the leaves of the leaf pairs 316 in the third group,along with the movement of the leaf pairs 316. In the process ofradiating the first non-zero fluence region A and the left half of thirdnon-zero fluence region C, part of the leaf pairs 313 which have alreadyfinished to play a part in radiating the first non-zero fluence region Aare shaded by the vertical jaw 330 under the downwardly movement of thevertical jaw 330, in sequence.

Specifically, referring to FIG. 5(b), the leaf pairs 313, 316 move alonga direction from left to right gradually. The first non-zero fluenceregion A and the left half of the third non-zero fluence region C areradiated through the opening between the leaves in the leaf pairs 313,316. Referring to FIG. 5(c), the uppermost leaf pair 313 a, which hasalready finished to play a part in radiating the uppermost part of thefirst non-zero fluence region A, is partially shaded by the vertical jaw330, along with the downwardly movement of the vertical jaw 330.Referring to FIG. 5(d), upper leaf pairs of the leaf pairs 313, whichhave finished to play a part in radiating the upper portion of firstnon-zero fluence region A, are shaded by the vertical jaw 330, alongwith the further downwardly movement of the vertical jaw 330. The firstnon-zero fluence region A and the left half of the third non-zerofluence region C continue to be radiated through the opening between theleaves of the unshaded leaf pairs 313 in the first group and the leafpairs 316 in the third group. Referring to FIG. 5(e), the vertical jaw330 continues to move downwardly till arriving at a bottom of the firstnon-zero fluence region A. The first group of leaf pairs 313 arecompletely shaded by the vertical jaw 330 at that moment. The firstnon-zero fluence region A and a left half of the third non-zero fluenceregion C are radiated completely.

In the step 703, MLC continues to move along the direction from left toright, to carry a second group of the leaf pairs 315 to an initialposition Pb of the second non-zero fluence region B. The zero fluenceregion is prevented from being radiated when the leaf pairs 315 movefrom the first non-zero fluence region A to the second non-zero fluenceregion B, since the zero fluence region is shaded by the vertical jaw330 when the vertical jaw 330 arrives at the bottom of the firstnon-zero fluence region A, i.e., at a bottom of the zero fluence region.The leaf pairs 313 in the first group and the leaf pairs 315 in thesecond group are at least partly same.

In the step 704, the vertical jaw 330 is withdrawn upwardly to exposethe leaf pairs 315 which begin to play a part in radiating the secondnon-zero fluence region B in sequence, when the second non-zero fluenceregion B and right half of the third non-zero fluence region C areradiated. Once the MLC 310 arrives at the bottom of the first non-zerofluence region A, the MLC 310 begins to leave from the bottom. The endof step 702 and the beginning of the step 704 happen almost the sametime, with the MLC 310 and the vertical jaw 330 moving constantly.

Specifically, referring to FIGS. 5(e) and 5(f), the third non-zerofluence region C is radiated gradually through the lower part of theopening between the leaves in the leaf pairs 316 of the third group,along with the further rightward movement of the leaf pairs 316.Meanwhile, the second non-zero fluence region B begins to be radiatedand then is radiated gradually through the upper part of the openingbetween the leaves in the leaf pairs 315 in the second group, along withthe movement of the leaf pairs 315 and the upwardly movement of thevertical jaw 330. In the process of radiating the second non-zerofluence region B and the right half of the third non-zero fluence regionC, the vertical jaw 330 is withdrawn to expose part of the leaf pairs315 which begin to play a part in radiating the second non-zero fluenceregion B, in sequence.

Referring to FIG. 5(f), the second non-zero fluence region B and theright half of third non-zero fluence region C continue to be radiatedthrough the opening between the leaves of the rest leaf pairs 315 of thesecond group and between the leaves of the leaf pairs 316 of the thirdgroup. Referring to FIG. 5(g), the second non-zero fluence region B andthe third non-zero fluence region C are radiated completely. Thevertical jaw 330 moves to a top of the second non-zero fluence region Band the second group of leaf pairs 315 are completely exposed from thevertical jaw 330. FIG. 5(g) shows final positions of the leaf pairs 315,316 when the fluence map has completely radiated. From the step 701 tothe step 704, the leaf pairs 316 in the third group are not shaded bythe vertical jaw 330.

In FIGS. 5(a)˜5(g), the vertical dimension of the first non-zero fluenceregion A is same to that of second non-zero fluence region B. The numberof the leaf pairs 313 in the first group is identical to that of theleaf pairs 315 in the second group. Optionally, the vertical dimensionof the first non-zero fluence region A can be different from that ofsecond non-zero fluence region B. When the vertical dimension of thefirst non-zero fluence region A is greater than that of second non-zerofluence region B, the number of the leaf pairs 313 in the first group ismore than that of the leaf pairs 315 in the second group. When thevertical dimension of the first non-zero fluence region A is smallerthan that of second non-zero fluence region B, the number of the leafpairs 313 in the first group is less than that of the leaf pairs 315 inthe second group. The above relationship between the leaf pairs 313 and315 can be applied not only in the first embodiment, but also can beapplied in the following second embodiment and the third embodiment.

FIG. 8 is a flowchart showing a process of radiating anothersubstantially U-shaped fluence map having a zero fluence region referredin a second embodiment. The fluence map in the second embodiment, asshown in FIG. 7, comprises a first non-zero fluence region A and asecond non-zero fluence region B, lack of a third non-zero fluenceregion.

In a step 801, a first group of leaf pairs in the second embodimentutilizable in radiating the first non-zero fluence region A are moved toan initial position of the first non-zero fluence region A.

In the step 802, the first non-zero fluence region is radiated from leftto right gradually through the opening between the leaves of the leafpairs in the first group, along with the movement of the leaf pairs inthe first group and the downwardly movement of the vertical jaw 330. Inthe process of radiating the first non-zero fluence region A, part ofthe leaf pairs 313 which have already finished to play a part inradiating the first non-zero fluence region A are shaded by the verticaljaw 330 under the downwardly movement of the vertical jaw 330, insequence.

In the step 803, the MLC 310 continues to move along the direction fromleft to right, to carry a second group of the leaf pairs of the MLC toan initial position of the second non-zero fluence region B. The zerofluence region is prevented from being radiated when the leaf pairs movefrom the first non-zero fluence region A to the second non-zero fluenceregion B, since the zero fluence region is shaded by the vertical jawwhen the vertical jaw 330 arrives at the bottom of the first non-zerofluence region A, i.e., at a bottom of the zero fluence region.

In the step 804, the vertical jaw is withdrawn upwardly to expose theleaf pairs which begin to play a part in radiating the second non-zerofluence region B in sequence, when the second non-zero fluence region Bis radiated. Once the MLC 310 arrives at the bottom of the firstnon-zero fluence region A, the MLC 310 begins to leave from the bottom.The end of step 802 and the beginning of the step 804 happen almost thesame time, with the MLC 310 and the vertical jaw 330 moving constantly.

A fluence map (not shown) in a third embodiment is similar to that inthe first embodiment, except that the zero fluence region between thefirst non-zero fluence region and the second non-zero fluence region inthe third embodiment has a substantially flat bottom edge to make amiddle part of the third non-zero fluence region below the flat bottomedge not aligned with the first non-zero fluence region or the secondnon-zero fluence region. An additional step 903 of radiating the middlepart of the third non-zero fluence region C with the vertical jaw 330remaining static is added.

FIG. 9 is a flowchart showing a process of radiating the substantiallyU-shaped fluence map having the zero fluence region referred in thethird embodiment. In the step 901, a first group of leaf pairsutilizable in radiating the first non-zero fluence region A are moved toan initial position of the first non-zero fluence region A. A thirdgroup of leaf pairs utilizable in radiating a left half of the thirdnon-zero fluence region C are moved to a left edge of the third non-zerofluence region C.

In the step 902, the first non-zero fluence region A and the left halfof the third non-zero fluence region C are radiated from left to rightgradually, along with the movement of the leaf pairs. In the process ofradiating the first non-zero fluence region A and the left half of thirdnon-zero fluence region C, part of the leaf pairs 313 which have alreadyfinished to play a part in radiating the first non-zero fluence region Aare shaded by the vertical jaw 330 under the downwardly movement of thevertical jaw 330, in sequence.

When the vertical jaw 330 arrives at a bottom of the first non-zerofluence region A, the step 903 is taken. In the step 903, only themiddle part of the third non-zero fluence region C is radiated, with theleaf pairs moving rightward and the vertical jaw 330 remaining static.

In the step 904, the MLC 310 continues to move along the direction fromleft to right, to carry the second group of the leaf pairs 315 to aninitial position of the second non-zero fluence region B. The zerofluence region is prevented from being radiated when the leaf pairs movefrom the first non-zero fluence region A to the second non-zero fluenceregion B, since the zero fluence region is shaded by the vertical jaw330 when the vertical jaw 330 arrives at the bottom of the firstnon-zero fluence region A, i.e., at a bottom of the zero fluence region.

In the step 905, the vertical jaw 330 is withdrawn upwardly to exposethe leaf pairs which begin to play a part in radiating the secondnon-zero fluence region B in sequence, when the second non-zero fluenceregion B and right half of the third non-zero fluence region C areradiated.

In a fourth embodiment, the fluence map is formed in a substantiallyX-shape has two zero-fluence regions. A process of radiating asubstantially X-shaped fluence map shown in FIG. 2(c) is illustratedbelow. Two vertical jaws 330 are used in shading the upper leaves andlower leaves of MLC 310.

FIG. 10 is a flowchart showing a process of radiating the substantiallyX-shaped fluence map, as shown in FIG. 2(c), having two zero fluenceregions referred in the fourth embodiment). In a step 711, a first groupof leaf pairs utilizable in radiating the non-zero fluence region S4 aremoved to an initial position of the non-zero fluence region S4, and afourth group of leaf pairs utilizable in radiating the non-zero fluenceregion S6 are moved to an initial position of the non-zero fluenceregion S6. A third group of leaf pairs utilizable in radiating a lefthalf of the non-zero fluence region S8 are moved to a left edge of thenon-zero fluence region S8.

In the step 712, the non-zero fluence region S4 is radiated from left toright gradually through the opening between the leaves of the leaf pairs313 in the first group, along with the movement of the first group ofleaf pairs and the downwardly movement of the first vertical jaw.Meanwhile, the non-zero fluence region S6 is radiated from left to rightgradually through the opening between the leaves of the leaf pairs inthe fourth group, along with the movement of the fourth group of leafpairs and the upwardly movement of the second vertical jaw. In the aboveprocess, the left half of the non-zero fluence region S8 is radiatedfrom left to right gradually. In the process of radiating the non-zerofluence region S4 and the non-zero fluence region S6, part of the leafpairs which have already finished to play a part in radiating thenon-zero fluence region S4 are shaded by the first vertical jaw underthe downwardly movement of the first vertical jaw, and part of the leafpairs which have already finished to play a part in radiating thenon-zero fluence region S6 are shaded by the second vertical jaw underthe upwardly movement of the second vertical jaw, in sequence.

In the step 713, a second group of the leaf pairs are moved to aninitial position of the non-zero fluence region S5 and a fifth group ofthe leaf pairs are moved to an initial position of the non-zero fluenceregion S7. The zero fluence regions are shaded by the first and secondjaws and thereby prevented from being radiated.

In the step 714, the first vertical jaw is withdrawn upwardly to exposepart of the second group of leaf pairs which begin to play a part inradiating the non-zero fluence region S5, the second vertical jaw iswithdrawn downwardly to expose part of the fifth group of leaf pairswhich begin to play a part in radiating the non-zero fluence region S7.

If there is only one zero-fluence region in the fluence map, the fluencemap can be formed into a U shape opened upwardly as shown in FIG. 2(b)or downwardly, or a C shape opened rightward or leftward, or a closed Oshape. The leaves of MLC 310 move repeatedly along a left-to-rightdirection, perpendicular to a top-to-bottom direction. If there aremultiple zero-fluence regions in the fluence map, the shape of thefluence map becomes complicated. The C-shaped fluence map, or O-shapedfluence map, or the complicated fluence map having multiple zero-fluenceregions in a fifth embodiment can be divided into multiple basic fluencemaps. Examples of dividing the C-shaped fluence map, O-shaped fluencemap, and the complicated fluence map are respectively illustrated below.

FIGS. 11(a)-11(c) show a C-shaped fluence map divided into several basicfluence maps. The C-shaped fluence map shown in FIG. 11(a), for example,can be divided into two substantially U-shaped basic fluence mapsrespectively shown in FIGS. 11(b) and 11(c). The substantially U-shapedfluence map shown in FIG. 11(b) contains all the fluence distributed inregion A, region B, and half of the fluence distributed in region C. Thesubstantially U-shaped fluence map shown in FIG. 11(c) contains all thefluence distributed in region D, region E, and half of the fluencedistributed in region C.

FIGS. 12(a)-12(c) show an O-shaped fluence map divided into severalbasic fluence maps. The O-shaped fluence map shown in FIG. 12(a), forexample, can be divided into two substantially U-shaped fluence mapsrespectively shown in FIGS. 12(b) and 12(c). The substantially U-shapedfluence map shown in FIG. 12(b) contains all the fluence distributed inregion A, region B, and half of the fluence distributed in region C. Thesubstantially U-shaped fluence map shown in FIG. 12(c) contains all thefluence distributed in region D, and half of the fluence distributed inregion C.

FIG. 13(a) shows a fluence map having a complicated shape and dividedinto several basic fluence maps shown in FIGS. 13(b)-13(d). The fluencemap shown in FIG. 13(a) comprises a U-shaped region, an O-shaped regionand a C-shaped region, and for example can be divided into three basicfluence maps, i.e., one substantially X-shaped basic fluence map and twosubstantially U-shaped basic fluence maps. The substantially X-shapedfluence map shown in FIG. 13(b) contains all the fluence distributed inregion A, region B, region C, region D, and half of the fluencedistributed in region E. The substantially U-shaped basic fluence mapshown in FIG. 13(c) contains half of the fluence distributed in regionE, half of the fluence distributed in region G, all the fluencedistributed in region F and region H. The substantially U-shaped fluencemap shown in FIG. 13(d) contains half of the fluence distributed inregion G, all the fluence distributed in region I and region J.

The several basic fluence maps are connected in series. The movingdirections of the leaf pairs of one MLC 310 or two MLCs 310 areinvariable in radiating a same basic fluence map and need to beconverted in different basic fluence maps, which are divided from theO-shaped fluence map, or the C-shaped fluence map, or the fluence maphaving complicated shape. An initial moving direction of the leaf pairsneeds to be determined firstly. For example, when the fluence map shownin FIG. 11(a) is radiated, the leaf pairs move from left to rightinvariably in radiating the basic fluence map shown in FIG. 11(b), andthen move from right to left invariably in radiating the next basicfluence map shown in FIG. 11(c). When the fluence map shown in FIG.12(a) is radiated, the leaf pairs move from left to right invariably inradiating the basic fluence map shown in FIG. 12(b), and then move fromright to left invariably in radiating the next basic fluence map shownin FIG. 12(c). When the fluence map shown in FIG. 13(a) is radiated, theleaf pairs move from left to right invariably in radiating the initialbasic fluence map shown in FIG. 13(b), then move from right to leftinvariably in radiating the next basic fluence map shown in FIG. 13(c),and finally move from left to right invariably in radiating the finalbasic fluence map shown in FIG. 13(d).

FIG. 14 is a flowchart showing a process of radiation method of thefifth embodiments of the present invention.

In the step 1101, a plurality of basic fluence maps are divided from thefluence map having at least one zero-fluence region. The basic fluencemap is referred to the convex-shaped basic fluence map shown in FIG.2(a), or the substantially U-shaped fluence map referred in the firstthrough the third embodiment, or the substantially X-shaped fluence mapreferred in the fourth embodiment shown in FIG. 2(c). The basic fluencemap can be radiated once along an invariable direction. In the step1102, each basic fluence map is radiated.

Specifically, when the basic fluence map is convex-shaped shown in FIG.2(a), the convex-shaped basic fluence map is radiated once when the MLC310 is moved along the invariable direction, without the participationof the vertical jaw. The step 1102 includes the step of radiating thebasic fluence map directly under the movement of the MLC 310.

When the basic fluence map is substantially U-shaped, the substantiallyU-shaped basic fluence map in the first through third embodiment isradiated once when the MLC 310 is moved along the invariable direction,along with the movement of the vertical jaw 330. Referring to FIGS. 6and 5(a), the first group of leaf pairs 313 utilizable in radiating thefirst non-zero fluence region A are moved to an initial position Pa ofthe first non-zero fluence region A.

The first non-zero fluence region A is radiated from left to rightgradually through an upper part of the opening between the leaves of theleaf pairs 313 in the first group, along with the movement of the leafpairs 313 and the downwardly movement of the vertical jaw 330. In theprocess of radiating the first non-zero fluence region A, part of theleaf pairs 313 which have already finished to play a part in radiatingthe first non-zero fluence region A are shaded by the vertical jaw 330under the downwardly movement of the vertical jaw 330, in sequence.

Referring to FIG. 5(b), the leaf pairs 313, 316 move along a directionfrom left to right gradually. The first non-zero fluence region A isradiated through the opening between the leaves in the leaf pairs 313.Referring to FIG. 5(c), the uppermost leaf pair 313 a, which has alreadyfinished to play a part in radiating the uppermost part of the firstnon-zero fluence region A, is partially shaded by the vertical jaw 330,along with the downwardly movement of the vertical jaw 330. Referring toFIG. 5(d), the upper leaf pairs of the leaf pairs 313, which havefinished to play a part in radiating the upper portion of first non-zerofluence region A, are shaded by the perpendicular jaw 330, along withthe further downwardly movement of the vertical jaw 330. The firstnon-zero fluence region A continue to be radiated through the openingbetween the leaves of the unshaded leaf pairs of the leaf pairs 313 inthe first group. Referring to FIG. 5(e), the vertical jaw 330 continuesto move downwardly till arriving at a bottom of the first non-zerofluence region A. The first non-zero fluence region A is completelyshaded by the vertical jaw 330 at that moment. The first non-zerofluence region A is radiated completely.

MLC continues to move along the direction from left to right, to carrythe leaf pairs 315 in the second group to an initial position Pb of thesecond non-zero fluence region B. The zero fluence region is preventedfrom being radiated when the leaf pairs 315 move from the first non-zerofluence region A to the second zero fluence region B, since the zerofluence region is shaded by the vertical jaw 330 when the vertical jaw330 arrives at the bottom of the first non-zero fluence region A, i.e.,at a bottom of the zero fluence region.

The vertical jaw 330 is withdrawn upwardly from the leaf pairs 315gradually in radiating the second non-zero fluence region B.

Referring to FIGS. 5(e) and 5(f), the second non-zero fluence region Bbegins to be radiated and then is radiated gradually through the openingbetween the leaves in the leaf pairs 315 in the second group, along withthe movement of the leaf pairs 315 and the upwardly movement of thevertical jaw 330. In the process of radiating the second non-zerofluence region B, the vertical jaw 330 is withdrawn to expose part ofthe leaf pairs 315 which begin to play a part in radiating the secondnon-zero fluence region B, gradually.

Referring to FIG. 5(f), the second non-zero fluence region B continuesto be radiated through the opening between the leaves of the rest leafpairs 315 in the second group. Referring to FIG. 5(g), the vertical jaw330 moves to a top of the second non-zero fluence region B and thesecond non-zero fluence region B is completely exposed from the verticaljaw 330. FIG. 5(g) shows final positions of the leaf pairs 315 when thebasic fluence map has been completely radiated.

The first and second non-zero fluence regions A, B are radiated only, orradiated together with the third non-zero fluence region C in the aboveprocess.

When the basic fluence map is substantially X-shaped, the steps 711-714are included.

The MLC 310 is moved repeatedly along the right-to-left direction inradiating different basic fluence maps.

As to a radiation method of radiating the fluence map, firstly, whetherthere is any zero-fluence region existed in the fluence map should beconsidered. If there is no zero-fluence region existed in the fluencemap, the fluence map can be radiated directly under the movement of theMLC 310.

If there is a zero-fluence region existed in the fluence map,determining one basic fluence map, i.e., the fluence map itself, ordividing a plurality of basic fluence maps connected in series from thefluence map as introduced in the step 1101, on consideration of theposition of the zero-fluence region.

A radiating step is taken then. When only one basic fluence map isdetermined, radiating the basic fluence map. When a plurality of basicfluence maps connected in series are divided from the fluence map, theplurality of basic fluence maps are radiated in sequence, under thecooperation of the MLC 310 and the vertical jaw 330. As to the fluencemap in the fifth embodiment, the fluence map should be divided intoseveral basic fluence maps in the dividing step 1101, and then the basicfluence maps are radiated one by one in the radiating step 1102.

The fluence map having U-shape, or X-shape, or C-shape, or O-shape, orother complicated shapes can be radiated once, rather than severaltimes. It doesn't need to close the radiation in the whole radiatingprocess. MU in the present invention is correspondingly reduced. Inaddition, it will be more efficiently to radiate the fluence map of thepresent invention, since the “set-up time” is saved. The treatment timemay be reduced accordingly. Furthermore, the fluence map is radiatedonce, therefore dose delivered at the edge of adjacent fluence region isaccurate.

As to the fluence map having more than one C-shaped fluence region orO-shaped fluence region, it will be more efficiently to use theconventional field-dividing method than the radiation method of thepresent invention, so it will be better to use the conventionalfield-dividing method to radiate the fluence map having more than oneC-shaped fluence region or O-shaped fluence region.

Although radiation is conducted by the prior jaws and MLC in the aboveembodiment, it can be understood by the one of skilled in the art that,the jaws herein can be replaced by other movable blocks substantiallynot transparent to X-rays.

The radiation method and apparatus used in radiating the fluence map inthe above embodiments of the present invention can be implemented bycomputer readable medium, such as software, hardware, or combination ofsoftware and hardware of computer. As for the implementation byhardware, the embodiment recited by the present invention can beimplemented by one or more ASIC (Application Specific IntegratedCircuit), DSP (Digital Signal Processing), DAPD (Distributed andParallel Database), PLD (Programmable Logic Device), FPGA (FieldProgrammable Gate Array), processors, controllers, microcontrollers,microprocessors, other electronic components for implementing theabove-mentioned function, or optional combinations of the abovecomponents. Under some circumstances, the embodiment can be implementedby controllers.

As to the implementation by software, the embodiment recited by thepresent invention can be implemented by independent modules, such asprocedure module and/or function module. Each independent module canimplement one or more functions or operations recited before. Thesoftware code can be implemented in an application programmed by properprogramming language, and can be stored in a memory, and implemented bycontroller or processor. For example, according to the presentinvention, a radiation apparatus used in radiating a fluence map havinga zero fluence region distributed along a moving direction of the leafpairs of MLC, or along a direction parallel to the moving direction ofthe leaf pairs of MLC.

The apparatus comprises a determining module and a driving module. Thedetermining module is used to determine one or more basic fluence mapsfrom the fluence map. The basic fluence map can be radiated once alongan invariable direction. The basic fluence map of a first style of shapecan be radiated under the movement of the MLC 310 directly, such as aconvex-shaped basic fluence map. The basic fluence map of a second styleof shape can be divided into zero fluence region and non-zero fluenceregions, and can be radiated by the cooperation MLC and one verticaljaw, such as the U-shaped basic fluence map, or can be radiated by thecooperation of MLC and two or more vertical jaws, such as X-shaped basicfluence map. The driving module is used in radiating the basic fluencemap of the second style of shape. The driving module is used to move theleaf pairs 313 of the first group to the initial position Pa of thefirst non-zero fluence region A, drive the leaf pairs 313, 316 move inthe first non-zero fluence region A and the third non-zero fluenceregion C, move the vertical jaw 300 along a direction perpendicular tothe moving direction of the leaf pairs 313 to shade the leaf pairs 313,drive the leaf pairs 315, 316 move in the second non-zero fluence regionA and the third non-zero fluence region C, and withdraw the vertical jaw330 from shading the leaf pairs 315 in radiating the second non-zerofluence region B.

Although the present invention is described in accordance with thecurrent specific embodiments, it is to be understood by one of skilledin the art that the above embodiments are illustrative of the principlesof the present invention. Other equivalent modifications orsubstitutions may also be employed without departing from the spirit ofthe present invention. Thus, various variations or modifications to theabove embodiment within the spirit of the present invention may bewithin the scope of the claims of the present application.

I claim:
 1. A method for radiating a target fluence map under a movementof a plurality of leaf pairs of a multi-leaf collimator (MLC),comprising: determining whether the target fluence map is a basicfluence map, wherein the basic fluence map is capable of being radiatedin a single radiation delivery by moving at least one portion of theplurality of leaf pairs to move in an invariable direction; in responseto a determination that the target fluence map is not a basic fluencemap, generating two or more basic fluence maps based on the targetfluence map, wherein at least two of the two or more basic fluence mapspartially overlap; and performing radiation of the two or more basicfluence maps in sequence.
 2. The method of claim 1, wherein at least oneof the two or more basic fluence maps includes a zero fluence regionlocated between two non-zero fluence regions in a movement direction ofthe plurality of leaf pairs.
 3. The method of claim 1, wherein each oneof the two or more basic fluence maps partially overlaps with one ormore other basic fluence maps of the two or more basic fluence maps. 4.The method of claim 1, wherein at least one of the two or more basicfluence maps is radiated based on a movement of a portion of theplurality of leaf pairs and a movement of one or more jaws.
 5. Themethod of claim 4, wherein the performing radiation of the two or morebasic fluence maps in sequence comprises: performing radiation of the atleast one basic fluence map, including: radiating a first portion of theat least one basic fluence map by moving a first group of leaf pairs ofthe plurality of leaf pairs in a first direction and moving a first jawin a second direction to shade the first group of leaf pairs insequence.
 6. The method of claim 5, wherein the performing radiation ofthe at least one basic fluence map further including: radiating a secondportion of the at least one basic fluence map by moving a second groupof leaf pairs of the plurality of leaf pairs in the first direction andmoving the first jaw in a third direction to expose the second group ofleaf pairs in sequence.
 7. The method of claim 6, wherein the seconddirection is perpendicular to the first direction.
 8. The method ofclaim 6, wherein the third direction is opposite to the seconddirection.
 9. The method of claim 6, wherein at least one leaf pairbelongs to both the first group of leaf pairs and the second group ofleaf pairs.
 10. The method of claim 6, wherein performing radiation ofthe at least one basic fluence map further including: radiating a thirdportion of the at least one basic fluence map by moving a third group ofleaf pairs of the plurality of leaf pairs in a fourth direction andmoving a second jaw in a fifth direction to shade the third group ofleaf pairs in sequence.
 11. The method of claim 10, wherein performingradiation of the at least one basic fluence map further including:radiating a fourth portion of the at least one basic fluence map bymoving a fourth group of leaf pairs of the plurality of leaf pairs inthe fourth direction and moving the second jaw in a sixth direction toexpose the fourth group of leaf pairs in sequence.
 12. The method ofclaim 11, wherein the fourth direction is the same as the firstdirection, the fifth direction is opposite to the second direction, andthe sixth direction is opposite to the third direction.
 13. The methodof claim 11, wherein at least a portion of the first portion of the atleast one basic fluence map and at least a portion of the third portionof the at least one basic fluence map are radiated simultaneously; or atleast a portion of the second portion of the at least one basic fluencemap and at least a portion of the fourth portion of the at least onebasic fluence map are radiated simultaneously.
 14. The method of claim1, further comprising: determining a radiation sequence of the two ormore basic fluence maps.
 15. The method of claim 1, wherein the two ormore basic fluence maps include a first basic fluence map and a secondbasic fluence map, the first basic fluence map and the second basicfluence map including an overlapping region, the overlapping regionhaving a target fluence, and the method further comprises: radiating theoverlapping region with half of the target fluence while radiating thefirst basic fluence map; and radiating the overlapping region with halfof the target fluence while radiating the second basic fluence map. 16.A method for radiating a target fluence map under a movement of aplurality of leaf pairs of a multi-leaf collimator (MLC), comprising:determining whether the target fluence map includes a zero fluenceregion between two non-zero fluence regions in a movement direction ofthe plurality of leaf pairs; in response to a determination that thetarget fluence map includes a zero fluence region between two non-zerofluence regions in a movement direction of the plurality of leaf pairs,performing radiation of the target fluence map by moving at least oneportion of the plurality of leaf pairs and moving a jaw based on amovement status of the at least one portion of the plurality of leafpairs.
 17. The method of claim 16, wherein the jaw is configured toprevent radiation of the zero fluence region during the movement of theat least one portion of the plurality of leaf pairs.
 18. The method ofclaim 16, wherein the performing radiation of the target fluence map bymoving at least one portion of the plurality of leaf pairs, and moving ajaw based on a movement status of the at least one portion of theplurality of leaf pairs comprises: radiating a first portion of thetarget fluence map by moving a first group of leaf pairs of theplurality of leaf pairs in a first direction and moving the jaw in asecond direction to shade the first group of leaf pairs in sequence; andradiating a second portion of the target fluence map by moving a secondgroup of leaf pairs of the plurality of leaf pairs in the firstdirection and moving the jaw in a third direction to expose the secondgroup of leaf pairs in sequence.
 19. The method of claim 18, wherein thesecond direction is perpendicular to the first direction, and the thirddirection is opposite to the second direction.
 20. An apparatus forradiating a target fluence map under a movement of a plurality of leafpairs of a multi-leaf collimator (MLC), comprising: a determining moduleconfigured to: determine whether the target fluence map is a basicfluence map, wherein the basic fluence map is capable of being radiatedin a single radiation delivery by moving at least one portion of theplurality of leaf pairs to move in an invariable direction; and inresponse to a determination that the target fluence map is not a basicfluence map, generate two or more basic fluence maps based on the targetfluence map, wherein at least two of the two or more basic fluence mapspartially overlap; and a driving module configured to drive one or moreleaf pairs of the plurality of leaf pairs to move to perform radiationof the two or more basic fluence maps in sequence.